Photovoltaic and Thermal Energy System With Improved Tracking

Abstract

An improved diurnal sun tracking system and methodology for use with a photovoltaic solar collector system mountable on flat roof industrial buildings or multi-unit apartment buildings is provided. The improved tracking system and method rotates or pivots the solar collector system to track the sun during the spring and fall Equinoxes in a first tracking mode, as well as from winter to summer solstices, when the angular rate of the sun's movement does not exactly follow the angular rate at the Equinoxes, in a second tracking mode.

1 . A system for improved sun tracking for use with roof-mounted solar collector modules, said system comprising:
 a roof-mounted solar collector module;   a stepper motor, mechanically coupled to the solar collector module, wherein the stepper motor is configured to pivot the solar collector module along a direction of movement of the sun;   a digital driver circuit electrically coupled to the stepper motor and configured to actuate the stepper motor;   a sensor configured to detect sun irradiance and, in response, provide an alignment signal corresponding to a current alignment of the solar collector module in relation to a position of the sun; and   a sun tracking circuit electrically coupled to the digital driver circuit and the sensor, wherein the sun tracking circuit is configured to:   receive the alignment signal from the sensor,   actuate the digital driver circuit according to a first mode when the alignment signal indicates that the current alignment of the solar collector module matches the position of the sun, and   actuate the digital driver circuit according to a second mode when the alignment signal indicates that the current alignment of the solar collector module does not match the position of the sun, wherein at least one of a speed and a direction of pivoting of the solar collector module is different in the second mode than in the first mode.   
     
     
         2 . The system of  claim 1 , wherein the speed of pivoting of the solar collector module in the second mode is faster than in the first mode. 
     
     
         3 . The system of  claim 1 , wherein the direction of pivoting of the solar collector module in the second mode is opposite the direction of movement of the sun. 
     
     
         4 . The system of  claim 1 , wherein the sun tracking circuit actuates the digital driver according to the first mode by providing clock pulses to the digital driver circuit at a rate of 1.04 seconds per step. 
     
     
         5 . The system of  claim 1 , wherein the sun tracking circuit actuates the digital driver according to the second mode by providing clock pulses to the digital driver circuit at a rate of 0.01 seconds per step. 
     
     
         6 . The system of  claim 1 , wherein the sun tracking circuit is further configured to detect a predetermined end of day time and, in response thereto, actuate the digital driver circuit to cause the stepper motor to pivot the solar collector module back to a start of day position. 
     
     
         7 . The system of  claim 1 , wherein the sensor comprises a first photocell and a second photocell, with a vane disposed there between. 
     
     
         8 . The system of  claim 7 , wherein the alignment signal indicates that the current alignment of the solar collector module matches the position of the sun when the first photocell detects a similar amount of sun irradiance as the second photocell. 
     
     
         9 . The system of  claim 7 , wherein the alignment signal indicates that the current alignment of the solar collector module does not match the position of the sun when the first photocell detects a substantially different amount of sun irradiance as the second photocell. 
     
     
         10 . The system of  claim 1 , further comprising a temperature sensor, electrically coupled to the sun tracking circuit, and configured to detect a current temperature of the solar collection module, and wherein the sun tracking circuit is further configured to cause the solar collector module to misalign from the sun when the current temperature exceeds a predetermined threshold temperature. 
     
     
         11 . A method for improved sun tracking for use with roof-mounted solar collector modules, the method comprising the acts of:
 detecting sun irradiance incident on a solar collector module, wherein the solar collection module is pivotable along a direction of movement of the sun by a stepper motor;   generating an alignment signal, based on said detecting, wherein the alignment signal correspond to a current alignment of the solar collector module in relation to a position of the sun;   actuating the stepper motor according to a first mode when the alignment signal indicates that the current alignment of the solar collector module matches the position of the sun;   actuate the stepper motor according to a second mode when the alignment signal indicates that the current alignment of the solar collector module does not match the position of the sun, wherein at least one of a speed and a direction of pivoting of the solar collector module is different in the second mode than in the first mode.   
     
     
         12 . The method of  claim 11 , wherein the speed of pivoting of the solar collector module in the second mode is faster than in the first mode. 
     
     
         13 . The method of  claim 11 , wherein the direction of pivoting of the solar collector module in the second mode is opposite the direction of movement of the sun. 
     
     
         14 . The method of  claim 11 , wherein actuating the stepper motor according to the first mode comprises actuating the stepper motor at a rate of 1.04 seconds per step. 
     
     
         15 . The method of  claim 11 , wherein actuating the stepper motor according to the second mode comprises actuating the stepper motor at a rate of 0.01 seconds per step. 
     
     
         16 . The method of  claim 11 , further comprising detecting a predetermined end of day time and, in response thereto, actuating the stepper motor to pivot the solar collector module back to a start of day position. 
     
     
         17 . The method of  claim 11 , wherein detecting sun irradiance comprises detecting sun irradiance on at least one of a first photocell and a second photocell having a vane disposed there between. 
     
     
         18 . The method of  claim 17 , wherein actuating the stepper motor according to the first mode comprises actuating the stepper motor according to the first mode when the first photocell detects a similar amount of sun irradiance as the second photocell. 
     
     
         19 . The method of  claim 17 , wherein actuating the stepper motor according to the second mode comprises actuating the stepper motor according to the second mode when the first photocell detects a substantially different amount of sun irradiance as the second photocell. 
     
     
         20 . The method of  claim 11 , further comprising:
 detecting a current temperature of the solar collection module; and   misaligning the solar collector module from the sun when the detected current temperature exceeds a predetermined threshold temperature.